1. Field of the Invention
The present invention relates to devices used on packers, bridge plugs and packoffs which are required to engage, anchor and seal inside a downhole casing or tubing.
2. Description of Related Art
Packers, bridge plugs, and packoff devices create an annular volume between a well casing and a well tubing, and provide a means to seal and block and/or direct flow of produced wellbore fluids. These devices are "set" by activating an anchoring mechanism, commonly referred to as a "slip" (or in plurality as "slips") to affix the device to the inside of the casing, and to compress a sealing member, commonly referred to as an "element", into sealable engagement with the inside wall of the casing. Typical embodiments of these devices include a conical wedge, driven with force under a slip, and are generally left in place for extended periods of time, and can be difficult to release due in part to the rigidity of the parts, the presence of corrosive well fluids and ambient debris. Time, heat from the well, debris and corrosion can cause the similar metallurgy to foul, lock, and/or bind together making retrieval of the packer from the well very difficult. Additionally, the cost of a downhole tool generally increases with the number of parts, the overall length, and design complexity. Reduction of parts translates to reduced cost, and increased reliability of the operational characteristics of the mechanism.
Specifically, in some packers a hydraulically operated piston is integral to the anchoring mechanism, and utilizes hydraulic pressure usually applied inside the tubing to activate the setting mechanism. Slips typically engage an interior surface of the well casing or tubing by a series of hardened teeth which lock the packer in position. These hydraulically set packers employ a concentric hydraulic piston, and pressure acting on such translates to an axial force, which in turn acts on an annular cone. The cone coacts with a mating conical surface on the slips. Axial movement of the cone causes the slips to move radially outward to engage the interior surface of the casing. This same axial movement of the hydraulic piston is commonly used to compress an elastomeric element array into sealable engagement with the inside diametrical wall of the casing. U.S. Pat. No. 5,146,994 discloses this configuration. Other and further methods of applying the axial force necessary to anchor and seal the device are shown in U.S. Pat. No. 5,086,839, whereby a set of drag springs are employed to set the disclosed packer; U.S. Pat. No. 5,095,979 discloses how a packoff may be deployed on coiled tubing and set using drag springs; U.S. Pat. No. 5,000,265 discloses how a packoff may be hydraulically set on coiled tubing; and U.S. Pat. No. 5,146,993, which illustrates a packing element utilized on packers, bridge plugs and packoffs.
While these applications, usage and configurations are novel and diverse, common constituent parts include a resilient packing element, at least one independent set of slips, with an interior conical surface that coacts with a separate exterior conical wedge. Axial motion is required to drive the conical wedge under the slips, which are, by such motion, driven radially outward into engagement with the tubing or casing. The interaction of this multiplicity of parts gives rise to the numerous problems described above.
There is a need for a novel, simplified sealing and anchoring device which reduces the number of parts to anchor and seal a packer, bridge plug or packoff in a well; and will maintain a reliable seal while set; and is more reliably retrieved than devices in current use.